Volumetric liquid-transfer device



Feb. 19, 1963 G. TAKATsY VOLUMETRIC LIQUID-TRANSFER DEVICE Filed- Nov. 21, 1961 INVEN OR. GYULA TAKZTSY ay sfi I 2 6- AGENT.

Unite Stat My present invention relates to improved volumetric liquid-transfer devices of a type suitable for use in quantitative and qualitative chemical analyses wherein relatively small quantities of a liquid are to be transferred from place to place with considerable accuracy as regards the amounts involved.

In my copending application Ser. No. 130,721 filed July 28, 1961, of which the instant application is a continuation-in-part, I have indicated that titrimetric techniques in, say, the quantitative analysis of components of a liquid frequently require successive dilutions of the liquid to be analysed and treatment of the diluate with predetermined quantities of reagent. Both the dilution of the liquid and the addition of reagent thereto may be effected with the aid of calibrated volumetric transfer devices. Hitherto, so-called transfer pipettes were about the only effective means for transferring relatively small or micro quantities of liquids with any degree of accuracy. These pipettes, which generally were glass tubes provided with a fine bore into which the liquid to be trans ferred was drawn by suction (e.g. by the application of the analysts mouth to the upper end of the pipette), had many disadvantages including the relatively awkward manipulatability of the pipettes, their large size coupled with low volume-transfer capabilities, and their lack of reproducibility for the transfer of different types of liquids.

-It is, therefore, an object of my invention to provide an improved liquid-transfer device of the character set forth adapted to' avoid the disadvantages of hitherto known volumetric'transfer apparatus.

. A further object of the instant invention is to provide a liquid-transfer device suitable for microanalyses with a high degree of reproducibility and adapted to transfer predetermined quantities of many different types of liquids while requiring only a minimum of calibration. 1 Still another object of the present invention is to provide a readily manipulatable volumetric liquid-transfer device of high mechanical stability.

. I have found that the above objects can be realized in a liquid-transfer device comprising a liquid-entrapping cage provided with capillary channels affording access to the interior of the cage and extending generally upwardly from the lower or forward portion of the cage as the latter is thrust downwardly into the liquid to be transferred with the aid of a stem or shank which, in order to maintain proper balance, is afiixed to the cage at a location along an axis of symmetry thereof along which lie the center of gravity of the cage and the apical region of its forward portion, the surface of the cage converging generally upwardly and outwardly from this apical region. The resulting device, whose stem advantageously extends substantially in its entirety along the aforementioned axis of symmetry, has been found to have excellent mechanical stability. The capillary channels of the cage should extend upwardly along substantially planar surfaces perpendicular to a plane transverse to the axis of symmetry and have portions extending generally in the direction of that axis. The arrangement set forth above renders the device capable of easily withstanding the jolts and ShOCks it encounters in normal use, in coutradistinction to arrangements, for example, wherein the shank is afiixed to the cage at a location 3,077,780 Patented Feb. 19, 1963 offset from the axis of symmetry of the cage which coincides, substantially, with a line joining the aforementioned apical region (which in generally spherical or hemispherical cage configurations constitutes the lower. polar region) with the center of gravity of the cage. Such offset arrangements, though previously considered practical, have now been found to be incapable of withstanding axial forces acting in the direction of the stem when, for instance, the apical region of the cage contacts the bottom of the liquid container.

While cages of many different configurations are possible within the definition given above, I have found that generally the cages should have the configurations of surfaces of revolution and, preferably, should intersect the axis at the bottom of the cage, i.e. at a location opposite its junction with the stern. Thus, generally spherical, hemispherical and, to a lesser extent, conical cages have been found to be especially effective and accurate.

The capillary channels, which in the case of aqueous and water-miscible liquids should have a width less than substantially 0.5 mm., must be sufiiciently wide to admit the liquid to be transferred into the interior of the cage so that any liquid entrapped in the cage will be prevented by the capillarity of the channels from emptying until the analyst using the device takes positive action (e.g. by shaking the device). The channels preferably lie along generatrices of the surface of revolution conforming to the configuration of the cage.

Yet another feature of the invention resides in the formation of the cage of the device from a plurality of elongated sheet-metal segments forming the surface of the cage while being secured together at their ends at axially spaced locations along the aforementioned axis of symmetry with sufficient angular spacing to form the capillary channels. The stem may be attachedto the cage at only one of these spaced locations but, if greater rigidity is desired, also may traverse the cage and'be' joined to it at both locations. To this end the stem can be provided with an annular plate, surrounding the axis and secured to the stem, which is provided Witha row of slots respectively receiving a tab formed at a corresponding end of each of the sheet-metal segments. The segments may be integral with each other at their other ends or similarly joined together by a further plate.

The above and other objects, features and advantages of the instant invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a cross-sectional view of a dilution plate showing a volumetric liquid-transfer device according to the invention in elevation;

FIG. 2 is a bottom-plan view of the device of FIG. 1;

FIG. 3 is an elevational View of an liquid-transfer de vice according to the invention;

FIG. 4 is a view similar to FIG. 3 of still another embodiment of the device;

FIG. 5 is a front-elevational view of yet another device according to the present invention; and

FIG. 6 is a side-elevational view of the device of FIG. 5.-

In FIG. 1 of the drawing 1 show part of a dilution plate 1 made from a readily washable material, such as porcelain or a synthetic resin, and provided with a plurality of relatively shallow recesses 2, one of which is shown on:

of a plurality of segments 12, constituted by upwardly 'bent sheet-metal segments interconnected at their lower ends, whose longitudinal edges define capillary channels 14 communicating with the inner cavity of the cage surrounded by the segments. The capillary channels advantageously have a width less than 0.5 mm. and, depending upon the capacity of the cage and the liquid to be transferred, may he as narrow as 0.05 mm. while the cage may have a capacity ranging upwards of about 0.01 ml. I have found that convenient values of the transfer capacity of the devices are 0.025, 0.05 and 0.1 ml. although other values equally practical may be made with suitable d1- mensioning of the cage 11. Ideally, the stem 18 and the cage 11 should be made from an inert, readily cleanable material such as platinum or one of its alloys (e.g. with iridium) which has the additional advantage of being easily sterilized in a flame without alteration of the transfer characteristics. Since the capacity of each device is dependent upon the volume of the inner cavity of the cage and the shape of the menisci formed along the capillary channels is substantially independent of the liquid, the capillary cage need be calibrated only once for precise transfer of substantially all liquids having similar meniscus shapes. The capillary cage 11 is filled by thrusting it below the surface 4 of the liquid 3, to an extent suflicient to create a pressure differential capable of breaching the capillarity barrier, any air within the cage being permitted to escape through slots 16 in the upper plate 15 thereof. The free ends of the cage segments 12 are formed with tabs 13 which are received in suitable slits in this plate. The apical region of the cage 12 is provided with a bore 17, whose diameter preferably does not exceed the maximum capillary'channel width, adapted to facilitate the introduction of liquid into the cage and its discharge therefrom.

From FIG. 1 is may be seen that the liquid level 4 corresponds to one of the aforedescribed transverse planes to which the substantially planar surfaces of the capillary channels 14 extend generally perpendicularly, this level being denoted by dot-dash lines 39, 49 and 60 in FIGS. 3-6. The plane of the liquid level extends perpendicularly to the axis of symmetry of the cage 12, which passes through the apical region and the center of gravity thereof, beyond the point of junction between the cage and its stem 18.

Upon withdrawal of the capillary cage from the liquid 3, the predetermined quantity contained within the cage may be transferred to another dilution recess 2 and admixed with the contents thereof by agitating the transfer device 10 with its cage immersed in the dilution liquid. Withdrawal of the device will again remove a predetermined quantity of now diluted liquid for further dilution in a similar manner.

In FIG. 3 I show a further volumetric transfer device 30 whose cage 31 is of generally spherical configuration with capillary channels 34, extending upwardly from the apical region 37 thereof, formed between segments 32 whose tabs 33 are received in suitable slits formed in the cover plate 35. The latter is annular and surrounds the stem 38 which passes through it and extends axially through the cage to its apical region 37, the stem lying wholly along the axis of symmetry of the cage while passing through its poles and center of gravity and being secured to the cage at the plate 35 and the apical region 37.

FIG. 4 illustrates another volumetric transfer device 40 wherein the stem 48 is secured axially to a capillary cage 41 of generally conical configuration formed by wall sections 42 whose spacings constitute capillary channels 44. The sections 42 converge upwardly and outwardly from the apical region 47 more sharply than do the segments 32 and 12 of the previously described embodiments so that the capillary cage 41 penetrates with great facility the surface skin of liquids into which it is thrust.

- The transfer device 50 of FIGS. and 6 is provided with a handle 59 which receives two shanks 58', 58", together forming a support stern, of a cage 51 of generally spherical configuration. The latter is formed by spiral coils 51, 52" of wire integral with their respective shanks 58', 58 and secured in base-to-base relationship by the handle 59. It will be readily apparent that in the embodiment of FIGS. 5 and 6, as in the previously described embodiments, the support stem lies along the axis of symmetry of the cage 51 which passes substantially through its center of gravity and its apex 57 and that the channels 52, 52" extending upwardly from the apical region lie along substantially planar surfaces substantially transverse to the plane 60, perpendicular to the stem at thepoint at which it merges into the cage, while having portions that extend in the general direction of the cage axis.

The invention as described and illustrated is believed to admit of many modifications and variations that will be readily apparent to persons skilled in the art and which are, accordingly, deemed to be included within the spirit and scope of the invention as claimed.

I claim:

1. A volumetric liquid-transfer device, comprising a liquid-entrapping cage having an axis of symmetry extending through an apical region thereof, the center of gravity of said cage lying substantially along said axis, said cage having an outer surface diverging upwardly and outwardly from said apical region and being provided with a plurality of throughgoing capillary channels having portions extending generally in the direction of said axis while communicating with the interior of said cage, and a stem secured to said cage at a location along said axis.

2. A volumetric liquid-transfer device, comprising a liquid-entrapping cage having an axis of symmetry extending through an apical region thereof, the center of gravity of said cage lying substantially along said axis, said cage having an outer surface diverging upwardly and outwardly from said apical region and being provided with a plurality of throughgoing capillary channels having portions extending generally in the direction of said axis while communicating with the interior of said cage, and a stem secured to said cage at a location along said axis and extending substantially in its entirety therealong.

3. A volumetric liquid-transfer device, comprising a liquid-entrapping cage having an axis of symmetry extending through an apical region thereof, the center of gravity of said cage lying substantially along said axis, said cage having an outer surface diverging upwardly and outwardly from said apical region and being provided with a plurality of throughgoing capillary channels having portions which lie in respective substantially planar surfaces perpendicular to a plane transverse to said axis, and a stem secured to said cage at a location along said axis.

4. A volumetric liquid-transfer device, comprising a liquid-entrapping cage having the configuration of a surface of revolution with an axis intersecting said surface at an apical region thereof, the center of gravity of said cage lying substantially along said axis, said cage having an outer surface diverging upwardly and outwardly from said apical region and being provided with a plurality of throughgoing capillary channels having portions extending generally in the direction of said axis while communicating with the interior of said cage, and a stern secured to said cage at a location along said axis.

5. A device according to claim 4 wherein said cage is of generally spherical configuration.

6. A device according to claim 4 wherein said cage is of generally semi-ellipsoidal configuration.

7. A device according to claim 4 wherein said channels extend along the turns of a spiral.

8. A device according to claim 4 wherein said channels extend along generat-rices of said surface of revolution.

9. A device according to claim 4 wherein said channels have a maximum Width of 0.5 mm.

10. A device according to claim 4 wherein said stem traverses said cage and is secured to said cage at said apical region.

11. A device according to claim 4 wherein said cage is provided with a plate disposed opposite said apical region and secured to said stem, said plate being provided with at least one opening adapted to facilitate the escape of from the interior of said cage.

12. A device according to claim 4 wherein said cage is provided with a bore at said apical region for facilirating the entry of liquid to be transferred into said cage.

13. A device according to claim 4 wherein said cage and said stem are composed of inert metallic material.

14. A device according to claim 13 wherein said material is selected from the group which consists of platinurn and its alloys.

15. A volumetric liquid-transfer device, comprising a liquid-entrapping cage having the configuration of a surface of revolution with an axis intersecting said surface at an apical region thereof, the center of gravity of said cage lying substantially along said axis, said cage having an outer surface diverging upwardly and outwardly from said apical region and being provided with a plurflity of throughgoing capillary channels having portions which lie in respective substantially planar surfaces perpendicular to a plane transverse to said axis, and a stem secured to said cage at a location along said axis.

16. A volumetric liquid-transfer device, comprising a liquid-entrapping cage having the configuration of a surface of revolution with an axis intersecting said surface at an apical region thereof, the center of gravity of said cage lying substantially along said axis, said cage having an outer surface diverging upwardly and outwardly from said apical region and being provided with a plurality of throughgoing capillary channels having portions extending generally in the direction of said axis while communicating with the interior [of said cage, and a stem secured to said cage at a location along said axis and extending substantially in its entirety therealong.

17. A volumetric liquid-transfer device, comprising a liqui-d-entrapping cage having the configuration of a surface of revolution with an axis intersecting said surface at an apical region thereof, the center of gravity of said cage lying substantially along said axis, said cage having an outer surface diverging upwardly and outwardly from said apical region and being provided with a plurality of throughgoing capillary channels having portions which lie in respective substantially planar surfaces perpendicular to a plane transverse to said axis, and a stern secured to said cage at a location along said axis and extending substantially in its entirety therealong.

18. A volumetric liquid-transfer device, comprising a liquid-entrapping cage of generally spherical configuration composed of two substantially symmetrical wire loops wound in spiral turns of progressively decreasing radius and progressively increasing distance from a common central plane along an axis of said cage transverse to said plane, and a handle for said cage including two elongated shanks integrally extending along said plane and in the plane of said axis from the largest turn of each of said loops, respectively, the turns of each of said loops being separated from one another by capillary channels giving access to the interior of said cage.

19. A device according to claim 18 wherein said handle further includes an elongated stem holding said shanks in closely juxtaposed relationship with each other.

20. A device according to claim 18 wherein said cage encompasses a volume ranging between substantially 0.01 and 0.1 milliliter.

References Cited in the file of this patent UNITED STATES PATENTS 2,137,773 Jones Nov. 22, 1938 2,410,045 Burk et al Oct. 29, 1946 2,868,020 Williams Ian. 13, 1959 

1. A VOLUMETRIC LIQUID-TRANSFER DEVICE, COMPRISING A LIQUID-ENTRAPPING CAGE HAVING AN AXIS OF SYMMETRY EXTENDING THROUGH AN APICAL REGION THEREOF, THE CENTER OF GRAVITY OF SAID CAGE LYING SUBSTANTIALLY ALONG SAID AXIS, SAID CAGE HAVING AN OUTER SURFACE DIVERGING UPWARDLY AND OUTWARDLY FROM SAID APICAL REGION AND BEING PROVIDED WITH A PLURALITY OF THROUGHGOING CAPILLARY CHANNELS HAVING PORTIONS EXTENDING GENERALLY IN THE DIRECTION OF SAID AXIS WHILE COMMUNICATING WITH THE INTERIOR OF SAID CAGE, AND A STEM SECURED TO SAID CAGE AT A LOCATION ALONG SAID AXIS. 